Edge illumination is necessary for a variety of different parts in a vehicle, such as in cup holders and in door illumination. Edge illumination can be achieved using a light active sheet that is described in more detail in U.S. Pat. No. 7,217,956 and in U.S. Patent Application Publication No. 2008/0079012, both of which are fully incorporated herein by reference. The light active sheet described in these documents is referred to in this disclosure simply as “light sheet” or “light sheet technology.”
FIG. 5 is a cross-section of related light sheet technology 501. In FIG. 5, the following x-y-z directions are utilized for ease of describing relationships of components. A light sheet can generally have a width from edge-to-edge (or a front-to-back direction) along direction x, a length from left side to right side (or a left-to-right direction) along direction y, and a top-bottom direction along direction z.
The light sheet 501 may include a first substrate 503, a second substrate 507, an adhesive layer 505 sandwiched between the first and second substrates, and a light emitting diode (LED) 517 that is embedded in the adhesive 505. First and second indium tin oxide (ITO) layers 509, 511 are sandwiched between the respective first and second substrates 503, 507 and the adhesive layer 505.
The first and second substrates 503, 507 may be transparent or clear substrates. The first and second substrates 503, 507 may be polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and/or polycarbonate. The first and second ITO layers 509, 511 can be provided as a coating on the respective first and second substrates 503, 507. The first and second substrates 503, 507 in combination with the first and second ITO layers 509, 511 form top and bottom electrically conductive transparent substrates. The adhesive layer can be a non-conductive transparent adhesive material.
The LED 517 can be one of plural LEDs. The LED 517 has a top surface which is perpendicular to a planar surface of the first substrate 503. When powered, the LED 517 emits photons 521 principally from the top surface (sometimes referred to as a “light emitting surface”). Because the top surface of the LED 517 is perpendicular to a planar surface of the first substrate 503, the light photons 521 are emitted generally up and through the first substrate 503 from the LED 517. The LED 517 is illustrated with photons being emitted.
Also illustrated in FIG. 5 is a first positive (+) copper bus 513 and second negative (−) copper bus 515 which power the ITO layers 509, 511 and thus power the LED 517. The LED 517 is representative of plural LEDs disposed along a left-to-right (y) direction. The layered structure of the light sheet typically is extended along a front-to-back direction to include plural LEDs. The basic structure of this light active sheet material is disclosed in more detail in U.S. Pat. No. 7,217,956 referenced above.
The above described light sheet is quite useful and efficient in producing light when viewed from above in the z direction. However, such a light sheet requires relatively larger amounts of space for placement. Therefore, the light sheet described above would not be particularly useful in edge lighting.
In order to modify the light sheet described above for edge lighting, the photons must be emitted in some manner in a front-to-back direction which is indicated as being in the x direction in FIG. 5. One approach to forcing the photons to move in the x direction is seen in U.S. Patent Application Publication Nos. 2013/0026504 and 2013/0027955, which are also expressly incorporated herein by reference. In these documents, the disclosed approach to redirecting photons is to provide additional layers of film that reflect the photons in the desired direction. However, adding film layers to the light sheet expands the size of the sheet as well as the costs of production of the light sheet.
The embodiments disclosed herein offer a simpler, less costly, and much more efficient approach to emitting photons in a front-to-back direction from a light sheet configured in a bottom-to-top direction. Specifically, one or more laser diodes are used which produce a highly concentrated photon emission in a front-to-back (x) direction. The use of a laser diode in a light sheet can produce a luminous intensity that is greater than the luminous intensity provided by the solutions described in the applications mentioned above by a factor of 1,000.